Apparatus and method for active vibration control of hybrid electric vehicle

ABSTRACT

A method for active vibration control of a hybrid electric vehicle may include: selecting a reference angle signal based on position information of a motor or an engine; generating a reference angle based on information of the reference angle signal; setting up a period of fast Fourier transform (FFT) and analyzing the FFT signal; setting up a reference spectrum according to an engine speed and an engine load; extracting a vibration component from each frequency based on information of the reference spectrum; selecting and adding a removal object frequency from the vibration of each frequency and performing inverse FFT; determining a basic amplitude ratio according to the engine speed and the engine load and an adjustable rate according to the engine load; and performing active vibration control of each frequency based on the information of the basic amplitude ratio, the adjustable rate, and the engine torque.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority to and the benefit of Korean PatentApplication No. 10-2015-0177480, filed on Dec. 11, 2015, which isincorporated herein by reference in its entirety.

FIELD

The present disclosure relates to an apparatus and a method for activevibration control of a hybrid electric vehicle.

BACKGROUND

The statements in this section merely provide background informationrelated to the present disclosure and may not constitute prior art.

A hybrid vehicle is a vehicle using two or more different kinds of powersources, and is generally a vehicle that is driven by an engine thatobtains a driving torque by burning fuel and a motor that obtains adriving torque with battery power.

Hybrid electric vehicles can be provided with optimum output torque,depending on how the engine and the motor are operated while thevehicles are driven by the two power sources, that is, the engine andthe motor.

Hybrid electric vehicles may form various structures using the engineand the motor as power sources, and hybrid electric vehicles areclassified as a TMED (Transmission Mounted Electric Device) type, inwhich the engine and the motor are connected by an engine clutch and themotor is connected to the transmission, and an FMED (Flywheel MountedElectric Device) type, in which the motor is directly connected to acrankshaft of the engine and connected to the transmission through aflywheel.

From among these, since the FMED type of the hybrid electric vehicle isvery noisy and has severe vibration, vibration reduction is beingstudied. A method of frequency analysis which extracts the vibrationcomponent is normally used for this.

An analog method using a band pass filter has been used in aconventional frequency analysis, and the analog method of analysisdetermines whether or not a frequency is abnormal based on an amplitudeof each expected point of a frequency band.

However, distinguishing between the vibration component of the engineand the vibration of the noise component is difficult, and unnecessaryover-control of the vibration negatively affects control efficiency andenergy management. Further, because it is only possible to create andsynchronize a reference signal with respect to a specific frequency inthe conventional frequency analysis, comprehensive and active control ofother frequencies which may be additionally generated is not performed.

SUMMARY

The present disclosure provides an apparatus and a method for activevibration control of a hybrid electric vehicle, having advantages ofelaborately controlling an abnormal vibration component through anentire frequency spectrum analysis using FFT (fast Fourier transform)and reflecting a change of a surrounding frequency component in realtime by feedback.

One form of the present disclosure provides a method for activevibration control of a hybrid electric vehicle that may include:selecting a reference angle signal based on position information of amotor or an engine; generating a reference angle based on information ofthe reference angle signal; setting up a period of fast Fouriertransform (FFT) and analyzing the FFT signal; setting up a referencespectrum according to an engine speed and an engine load; extracting avibration component from each frequency based on information of thereference spectrum; selecting and adding a removal object frequency fromthe vibration of each frequency and performing inverse FFT; determininga basic amplitude ratio according to the engine speed and the engineload and an adjustable rate according to the engine load; and performingactive vibration control of each frequency based on the information ofthe basic amplitude ratio, the adjustable rate, and the engine torque.

The reference angle may be set by dividing by a number (m) of resolverpoles based on information of the position of the motor or set up thereference angle between top dead center (TDC) of the number one cylinderand bottom dead center (BDC) of the number four cylinder based oninformation of the position of the engine.

The FFT period may be set in consideration of a cylinder and a stroke ofthe engine.

The analysis of the FFT signal may calculate a magnitude and phaseinformation of each frequency.

The vibration component of each frequency may be extracted by comparingthe reference spectrum with the FFT signal analysis result.

The vibration component may be removed by summing a reference signalobtained by inverse FFT and a value found by multiplying the enginetorque and the basic amplitude ratio and the adjustable rate in theactive vibration control of each frequency.

The adjustable rate according to the engine load may be determined todecrease an anti-phase torque when the engine load is greater than orequal to a predetermined load.

Another exemplary form of the present disclosure provides a controlapparatus for active vibration control of a hybrid electric vehicleincluding an engine and a motor as a power source. The control apparatusmay include: a position sensor configured to detect position informationof the engine or the motor; and a controller configured to select areference angle signal on the basis of a signal from the positionsensor, perform fast Fourier transform (FFT) analysis by generating areference angle, extract a vibration component of each frequency throughthe FFT analysis, generate a reference signal by performing inverse FFT,and perform active vibration control of each frequency by reflecting abasic amplitude ratio, an adjustable rate according to an engine load,and an engine torque to the reference signal.

The controller may set up a reference spectrum according to a speed andload of the engine, and extract a vibration component of each frequencyby comparing the reference spectrum with the FFT signal analysis result.

The controller may generate a reference signal by performing inverse FFTafter selecting and summing a removal object frequency from eachfrequency vibration through FFT analysis.

The controller may remove the vibration component by summing thereference signal generated by the inverse FFT and a value found bymultiplying the basic amplitude ratio, the adjustable rate, and theengine torque.

The controller may set up the reference angle by dividing by a number(m) of resolver poles based on information of the position of the motoror set up the reference angle between top dead center (TDC) of a numberone cylinder and bottom dead center (BDC) of a number four cylinderbased on information of the position of the engine.

The controller may set up an FFT period in consideration of a cylinderand stroke of the engine, and analyzes the FFT signal by a calculatedmagnitude and phase information of each frequency.

The controller may determine the adjustable rate according to the engineload to decrease an anti-phase torque when the engine load is greaterthan or equal to a predetermined load.

As described above, the vibration may be actively controlled, becausethe exact vibration component of each frequency may be extracted throughFFT frequency spectrum analysis. Therefore, since the determinationsystem of the reference angle of the engine and the motor may beutilized as it is, an additional device or an algorithm for signalsynchronization as used in the conventional art may be eliminated.

In addition, since the adjustment amount of vibration and frequencywhich is the object of the vibration control may be controlledindividually, it is possible to inhibit inefficienct energy consumptionwhich is from the control when the vibration is over-removed.Particularly, energy consumption during a high load region of the enginecan be reduced by decreasing an anti-phase torque comparing to a lowload region of the engine. Thus, precise and efficient active controlmay be performed through the feedback control in real time.

Further areas of applicability will become apparent from the descriptionprovided herein. It should be understood that the description andspecific examples are intended for purposes of illustration only and arenot intended to limit the scope of the present disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

In order that the disclosure may be well understood, there will now bedescribed various forms thereof, given by way of example, referencebeing made to the accompanying drawings, in which:

FIG. 1 is a schematic block diagram of an apparatus for active vibrationcontrol of a hybrid electric vehicle;

FIG. 2 is a flowchart illustrating a method for active vibration controlof a hybrid electric vehicle;

FIG. 3 is a drawing illustrating vibration reduction to which a methodfor active vibration control of a hybrid electric vehicle is applied incase that an engine load is high.

The drawings described herein are for illustration purposes only and arenot intended to limit the scope of the present disclosure in any way.

DETAILED DESCRIPTION

The following description is merely exemplary in nature and is notintended to limit the present disclosure, application, or uses. Itshould be understood that throughout the drawings, correspondingreference numerals indicate like or corresponding parts and features.

Throughout this specification and the claims which follow, unlessexplicitly described to the contrary, the word “comprise” and variationssuch as “comprises” or “comprising” will be understood to imply theinclusion of stated elements but not the exclusion of any otherelements.

It is understood that the term “vehicle” or “vehicular” or other similarterm as used herein is inclusive of motor vehicles in general includinghybrid vehicles, plug-in hybrid electric vehicles, and other alternativefuel vehicles (e.g., fuels derived from resources other than petroleum).As referred to herein, a hybrid electric vehicle is a vehicle that hastwo or more sources of power, for example both gasoline-powered andelectric-powered vehicles.

Additionally, it is understood that some of the methods may be executedby at least one controller. The term “controller” refers to a hardwaredevice that includes a memory and a processor configured to execute oneor more steps that should be interpreted as its algorithmic structure.The memory is configured to store algorithmic steps and the processor isspecifically configured to execute said algorithmic steps to perform oneor more processes which are described further below.

Furthermore, the control logic of the present disclosure may be embodiedas non-transitory computer readable media on a computer readable mediumcontaining executable program instructions executed by a processor, acontroller, or the like. Examples of computer readable media include,but are not limited to, ROM, RAM, compact disc (CD)-ROMs, magnetictapes, floppy disks, flash drives, smart cards, and optical data storagedevices. The computer readable recording medium can also be distributedin network coupled computer systems so that the computer readable mediaare stored and executed in a distributed fashion, e.g., by a telematicsserver or a controller area network (CAN).

FIG. 1 is a schematic block diagram of an apparatus for active vibrationcontrol of a hybrid electric vehicle according to one form of thepresent disclosure.

As shown in FIG. 1, an apparatus for active vibration control of ahybrid electric vehicle includes an engine 10, a motor 20, a positionsensor 25, a clutch 30, a transmission 40, a battery 50, and acontroller 60.

The engine 10 outputs power by combusting fuel as a power source whileturned on. The engine 10 may be a gasoline engine or a diesel engineusing conventional fossil fuel. The rotation power generated from theengine 10 is transmitted to the transmission 40 side through the clutch30.

The motor 20 may be operated by a 3-phase AC voltage applied from thebattery 50 through an inverter to generate torque, and operates as apower generator and supplies regenerative energy to the battery 50 in acoast-down mode.

In one form, the motor 20 may be directly connected to the crankshaft ofthe engine 10.

The position sensor 25 detects position information of the engine 10 orthe motor 20. That is, the position sensor 25 may include a crankshaftposition sensor that detects a phase of the crankshaft or a motorposition sensor that detects a position of a stator and a rotor of themotor.

The clutch 30 is disposed between the motor 20 connected to thecrankshaft of the engine 10 and the transmission 40, and switches powerdelivery to the transmission 40. The clutch 30 may be applied as ahydraulic pressure type of clutch or dry-type clutch.

The transmission 40 adjusts a shift ratio according to a vehicle speedand a running condition, distributes an output torque by the shiftratio, and transfers the output torque to the driving wheel, therebyenabling the vehicle to run. The transmission 40 may be applied as anautomatic transmission (AMT) or a dual clutch transmission (DCT).

The battery 50 is formed with a plurality of unit cells, and a highvoltage for providing a driving voltage to the motor 20 is stored at thebattery 50. The battery 50 supplies the driving voltage to the motor 20depending on the driving mode, and is charged by the voltage generatedfrom the motor 20 in the regenerative braking.

The controller 60 selects a reference angle signal on the basis of asignal from the position sensor 25, performs fast Fourier transform(FFT) analysis by generating a reference angle, extracts a vibrationcomponent of each frequency through the FFT analysis, and generates areference signal by performing inverse FFT.

After that, the controller 60 performs active vibration control of eachfrequency by reflecting a basic amplitude ratio, an adjustable rateaccording to an engine load, and an engine torque to the referencesignal.

For these purposes, the controller 60 may be implemented as at least oneprocessor that is operated by a predetermined program, and thepredetermined program may be programmed in order to perform each step ofa method for active vibration control of a hybrid electric vehicle.

Various forms described herein may be implemented within a recordingmedium that may be read by a computer or a similar device by usingsoftware, hardware, or a combination thereof, for example.

According to hardware implementation, the forms described herein may beimplemented by using at least one of application specific integratedcircuits (ASICs), digital signal processors (DSPs), digital signalprocessing devices (DSPDs), programmable logic devices (PLDs), fieldprogrammable gate arrays (FPGAs), processors, controllers,micro-controllers, microprocessors, and electric units designed toperform any other functions.

According to software implementation, forms such as procedures andfunctions described in the present forms may be implemented by separatesoftware modules. Each of the software modules may perform one or morefunctions and operations described in the present disclosure. A softwarecode may be implemented by a software application written in anappropriate program language.

Hereinafter, a method for active vibration control of the hybridelectric vehicle according to an exemplary form of the presentdisclosure will be described in detail with reference to FIG. 2 to FIG.3.

FIG. 2 is a flowchart illustrating a method for active vibration controlof a hybrid electric vehicle, and FIG. 3 is a drawing illustratingvibration reduction to which a method for active vibration control of ahybrid electric vehicle is applied in case that an engine load is high.

As shown in FIG. 2, an active vibration control method of the hybridelectric vehicle is started when the controller 60 selects the referenceangle signal based on the signal of the position sensor 25 at step S100.That is, the controller 60 selects the reference angle signal accordingto information of positions of the engine 10 and the motor 30.

When the reference angle signal is selected in the step S100, thecontroller 60 generates the reference angle at step S110. The controller60 may set up the reference angle by dividing by a number (m) ofresolver poles based on information of the position of the motor 20, ormay set up the reference angle between top dead center (TDC) of thenumber one cylinder and bottom dead center (BDC) of the number fourcylinder based on information of the position of the engine 10. Forexample, the controller 60 may select the reference angle based on theinformation of the position of the motor 20, and may create thereference angle by dividing 16 poles signal into eight (8).

After that, the controller 60 sets up a period of the FFT for performinganalysis of the FFT at step S120. The controller 60 may set up theentire period in consideration of a cylinder and stroke of the engine10. For example, if the engine 10 has four cylinders and four strokes,the crank angle may be 720 degrees.

When the FFT period is set up in the step S120, the controller 60analyzes the FFT signal at step S130. That is, the controller 60 maycalculate magnitude and phase information of each frequency by the FFTanalysis.

In addition, the controller 60 sets up a reference spectrum according tothe engine speed (engine rotation period) and the engine load at stepS140. That is, the controller 60 may set up a vibration reference valueof each frequency according to an operating point of the engine.

When the reference spectrum is set up in the step S140, the controller60 extracts a vibration component of each frequency at step S150. Thatis, the controller 60 may select an object requiring vibration controlin a compared result value of the FFT analysis and the predeterminedvibration reference value.

As shown in FIG. 3, a magnitude and phase of vibration components ofeach frequency calculated by performing FFT analysis is illustrated inleft upper side of the drawing.

When the vibration component of each frequency is extracted in the stepS150, the controller 60 selects and adds a frequency to be removed fromthe vibration of each frequency, and performs inverse FFT to generate areference signal at step S160.

In addition, the controller 60 determines a basic amplitude ratioaccording to the engine speed and the engine load and an adjustable rateaccording to the engine load at step S170. Herein, the basic amplituderatio according to the engine speed and load may be determined inadvance by a predetermined map. Also, the adjustable rate according tothe engine load may be determined to decrease an anti-phase torque whenthe engine load is greater than or equal to a predetermined load.

As shown in FIG. 3, the anti-phase torque which overlaps the componentof vibration to be removed is illustrated as a dotted line in left lowerside of the drawing. Herein, if the engine enters to a high load regionwhen the engine load is greater than or equal to a predetermined load,the adjustable rate may be set up such that the anti-phase torque isdecreased in a negative direction as illustrated by a solid line.

That is, since vibration of the engine is decreased in a high loadregion, energy consumption can be reduced instead of decreasing effectof vibration reduction.

After that, the controller 60 performs active vibration control based oninformation of the amplitude ratio, the adjustable rate, and the enginetorque at step S180. That is, the controller 60 may remove all thepositive components and negative components of the vibration componentsby summing a reciprocal value found by multiplying the reference signalcreated by inverse FFT and the engine torque and the basic amplituderatio and the adjustable rate.

As described above, according to the exemplary form of the presentdisclosure, the vibration may be actively controlled, because the exactvibration component of each frequency may be extracted through FFTfrequency spectrum analysis. Therefore, since the determination systemof the reference angle of the engine and the motor may be utilized as itis, an additional device or an algorithm for signal synchronization asused in the conventional art may be eliminated.

In addition, the adjustment amount of vibration and frequency which isthe object of the vibration control may be controlled individually, itis possible to inhibit inefficient energy consumption which is from thecontrol when the vibration is over-removed. Particularly, energyconsumption during a high load region of the engine can be reduced bydecreasing an anti-phase torque comparing to a low load region of theengine. Thus, precise and efficient active control may be performedthrough the feedback control in real time.

While this present disclosure has been described in connection with whatis presently considered to be practical exemplary forms, it is to beunderstood that the present disclosure is not limited to the disclosedforms. On the contrary, it is intended to cover various modificationsand equivalent arrangements included within the spirit and scope of thepresent disclosure.

What is claimed is:
 1. A method for active vibration control of a hybrid electric vehicle, the method comprising: selecting a reference angle signal by a controller based on position information detected by a position sensor, the position information including motor position information detected from a motor or engine position information detected from the engine; generating, by the controller, a reference angle corresponding to the reference angle signal; setting, by the controller, a period for applying a fast Fourier transform (FFT) based on an engine attribute of the engine; after the period for applying the FFT is set, analyzing, by the controller, a FFT signal based on performing the FFT on an engine speed or a motor speed during the period, the FFT signal comprised of a plurality of frequency components; determining a reference spectrum covering the plurality of frequency components by the controller based on the engine speed and an engine load of the engine; extracting vibration components by the controller from the FFT signal based on the comparison of the FFT signal with the reference spectrum; selecting a removal object frequency by the controller from the extracted vibration components; determining a reference signal based on performing an inverse FFT on the selected removal object frequency; determining a basic amplitude ratio by the controller based on the engine speed and the engine load, and determining an adjustable rate based on the engine load; and performing active vibration control on each of the plurality of frequency components using the controller by summing values calculated from the basic amplitude ratio, the adjustable rate, an engine torque, and the reference signal.
 2. The method of claim 1, wherein the reference angle is set by dividing by a number of resolver poles based on information of the position of the motor or set up the reference angle between a top dead center (TDC) of a number one cylinder and a bottom dead center (BDC) of a number four cylinder based on information of the position of the engine.
 3. The method of claim 1, wherein the period is set based on engine attributes including a number of cylinders of the engine and a stroke of the engine.
 4. The method of claim 1, wherein, in the step of analyzing the FFT signal, a magnitude and a phase of each of the plurality of frequency components are calculated.
 5. The method of claim 1, wherein the extracted vibration components are removed by summing the reference signal obtained by performing the inverse FFT and the calculated values obtained by multiplying the engine torque and the basic amplitude ratio and the adjustable rate.
 6. The method of claim 1, wherein the adjustable rate is determined to decrease an anti-phase torque when the engine load is greater than or equal to a predetermined load. 